Electric organ



Jan. 13, 1931. J. BETHENOD ELECTRIC ORGAN Filed April 22. 1929 :1) (DCDC 0 @l f @l 0, Q Q @l Q .C Q, @l Q l C @l .u 4o o u Q Q, y .www .MVA.a .n mi u xi 4 effe? Patented Jan. 13, 1931 NUNrriau) STATES PATENTIorificis:v

nnc'mfconcm, i

Anuman minimi as, im, semi lo. 357,194, mi in rma nay 1o, im.

My invention relates to a novel electric instrument or organ,electrically actuated by an arrangement of alternators of musicalfrequency and of very feeble power, of vari- 5 able reluctance type,coupled to a telephone loud speaker through a thermionic amplifier.

An object ofr m invention is to develop this fundamental idea in' aparticular man.- ner and to disclose embodiments which can l0 beadvantageously adopted to obtain an iiistrument sulliciently simple,robust and at low cost. l

' My invention will be more fully understood by reference to the annexeddrawing which represents an embodiment offan organ according to myinvention. Let it be assumed that thev problem is to produce eithersingly 'or in combination eighty-four different notes representing sevenoctaves. A motor 5 of any convenient type whose speed is. maintainedconstant b means of the regulator 6, which may be o any familiar type,drives the'shaft 7. The latter by meansof silent helicoidal gears 88 and8 itself drives twelve shafts such as 1, 1 and 1", etc. A tachometer 9serves to control the s eed of the entire group. Onl each one of tliesesecondary shafts there is mounted an alternator 10, 10', 10, vthe ratiosof gears 8, 8f and 8 being chosen in such mannerL that the correspondinf uencies shall be those of the scale in wichetlie lowest note is the Aof the sub-contra group, corresponding to approximately 27.18 vibrationsper second, which is practically the lowest frequency required in music.

F urthermoreyon each one of the shafts 1,

1, 1", there are mounted three other alter# nators whose frequencies arewith reference to those of the first in the ratios 2, 8, 32. All thesealternators are of homopolai' form having variable reluctance obtainedby rotatin an eccentric disc in the field. In some a ternators theentire periphery may 5 be occupied by active statorv elements,and

in other alternators onl a fractional part of the periphery, depen ingon the particular alternator, ma be so occupied. Of course the-olarticuar numbers mentioned 5 may be m 'fied according to the effects desired,and the number of secondary shafts and the number of alternators maybechosen as required. .f

In the circuit of alternator 10 there is 4connected a line switch 13, anoutput coil I5 31, an iron core inductance 14, and a limit- *ingimpedance coil 11. The iron core of inductance 14 is movable axially,thus varying the inductance. Key 12 controls" the circuit of alternator10 by closing the line 60 switch 12 and is attached to tlie iron core ofinductance 14 s0 that depressing key 12 withdraws a part of the ironcore from inductance 14. If ke 12 is lightly depressed, a note of lowintensity is obtained, 05 and as key 12 is depressed further, the noteintensity increases. The maximum intensity of each note may be limitedby the limiting impedance coil 11 which may be adjusted by the control15. Provision' may be made 70 to cha-nge the setting Aof control 15while he alternating current produced by the alternator 10 istransmitted to tuned circuit 17 for generating and controlling harmonicswhich include variable condensers 18 and 20 and variable self-inductancecoil 19.` These circuits are coupled to the input coil 21 of athermionic amplifier 22. The amplified currents are reproduced b loudspeakers 23 80 of an ordinary type, such asmoving coil. Trills oranalogous effects can be produced by yacting'periodically on thecircuits b means of a rapidly varying impedance suc as a rheostat orinductance. ma i have a rotating slider, the inductance coi ma be of thevariometer type and have a mova le rotor, and these may be controlled byhand or foot. The output of alternator 24 whose frequency is double thatof the 90 alternator 10 can be delivered to amplifier 22 and loudspeakers 23 by depressing key 27 or its output can be delivered toanother similar system of amplifiers and loud speakers representeddiagrammatically at 29 and 95 30, byfdepressing key 28.

According to my invention this second series of loud speakersrepresented at 30 is of a special type whichdoes not have direct currentexcitation or any permanent mag- 1" The rheostat net and -its motor unitreduces to a simple produces for an input frequency f, a musical note offrequency 2 an octave above the input frequency. onsequently since loudsakers 23 are of an ordinary type one will o tain, according as onedepresses key 27 or 28, either the note corresponding/to the frequenc ofalternator 24, or a note one octave higher. lAlternators 25 and 26 arearranged 1n the same manner as alternator 24 and can thus control asdesired either loud speakers 23, or loud speakers 30. It is thereforeevident that wit the four alter- 4 nators driven by the shaft 8 one canobtain seven notes which are in the ratios 1, 2, 4, 8, 16, 32, 64, thealternator 10 producing the note 1, the alternator 24 producing thenotes in the ratios 2 and 4, the alternator 25 producing the notes inthe ratios 8 andl, and the alternator 26 producing the notes in theratios 32 and 64.' The alternators mounted on the other shafts 1', 1,are connected to the amplifiers 22 and 29 by connections similar tothose Iconnecting the alternators of shaft 1.

There are thus obtained eighty-four notes from forty-eight alternators,while with the arrangements heretofore known it would have beennecessary to have eighty-four alternators to obtain the same result. Theresulting advantage of the invention is therefore considerable, thegreat number of alternators heretofore necessary being a seriousinconvenience of apparatus heretofore proposed of a similar ty It is tobe understood)e that the example shown in the drawing is not to beconsidered a limitation and it is evident that the invention can beeasily applied to cases in which the number of musical notes to beproduced is different.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is as follows:

1. An electric organ comprisingin combination a plurality of alternatorssynchronously driven at constant speed, means for amplifying thecurrents produced b said alternators, two separate systems of, loudspeakers adapted to be selectively supplied by said alternators, one ofsaid systems having loud speakers whose motors com rise alternatingcurrent electromagnets wit out continuous current excitation and,without permanent magnets, whereby the number of musical notes obtainedis greater ythan the number of said alternators.

2. In an electric organ, a plurality` ofI alternators of differentrequency characteristics driven synchronously at constant speed,therrnionic-amplifiers for amplifying the output of said alternators,individual line switches for selectively controlling the output circuitsof said alternators, two systems of loud s akers, one of said systemscomprisin lou s akersY deliverin a note correspon ing to t e frequencyof t e input current of said system, the other of said systemscomprising loud speakers driven by an alternating current electromagnet,and means for selectivelyl delivering to said loud Speaker systems theoutputs of said alternators.

3. In an electric or an, a plurality of alternators of differentrequency characteristics driven synchronously at constant speed,thermionic amplifiers for am lifyin the output of said alternators, inividua line switches for selectively controlling the output circuits ofsaid alternators, two systems of loud speakers, one of said systemscomprisin loud s akers deliverin a note correspon ing to t e frequencyof t e input current of said system, the other of said systemscomprising loud speakers delivering a note corresponding to twice thefrequency of the input current of said system, and means for selectivelydelivering to said loud speaker systems the outputs of said alternators.

4. In an electric organ, a plurality of alternators of differentfrequency characteristics driven synchronously at constant speed,thermionic amplifiers for am lifyin the output of said alternators, inividua yline switches for selectively controlling the output circuits ofsaid alternators, two systems of loud speakers, one of said systemscomprisin loud speakers-deliverin a note correspon ing to the frequencyof t e input current of said system the other of said systems comprisingloud speakers driven by an alternating current electromagnet, means forselectively delivering to said loud speaker systems the outputs of saidalternators, and individual rapidly variable impedances in the outputcircuit of each of said alternators for varying the output wave form ofsaid alternator.

JOSEPH BETHENOD.

